docker compose mounts volume for postgres by default

[GaryPWhite]

Description

• adds volume support for postgresql
• patches python3-pip dependency in dockerfile to python3-dev (explanation below)

This PR fixes #2676

Notes for Reviewers
The first file, the compose file, should be simple to follow with knowledge of volumes in docker. But why did I change the Dockerfile, you may wonder?

I've included a very-unrelated change from the original title and intent of this PR. I found this lil' nugget when I went to test my changes

  building 'backports.zoneinfo._czoneinfo' extension
  creating build/temp.linux-aarch64-cpython-38
  creating build/temp.linux-aarch64-cpython-38/lib
  gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -I/opt/venv/include -I/usr/local/include/python3.8 -c lib/zoneinfo_module.c -o build/temp.linux-aarch64-cpython-38/lib/zoneinfo_module.o -std=c99
  In file included from /usr/lib/gcc/aarch64-linux-gnu/8/include-fixed/syslimits.h:7,
                   from /usr/lib/gcc/aarch64-linux-gnu/8/include-fixed/limits.h:34,
                   from /usr/local/include/python3.8/Python.h:11,
                   from lib/zoneinfo_module.c:1:
  /usr/lib/gcc/aarch64-linux-gnu/8/include-fixed/limits.h:194:15: fatal error: limits.h: No such file or directory
   #include_next <limits.h>  /* recurse down to the real one */
                 ^~~~~~~~~~
  compilation terminated.
  error: command '/usr/bin/gcc' failed with exit code 1
  ----------------------------------------
  ERROR: Failed building wheel for backports.zoneinfo
Failed to build backports.zoneinfo

Output would occur whenever I built the dockerfile to run with docker compose, or when I built the file by itself. With a bit of sleuthing (ddg-ing) I found the littleist jupyterhub reported similar issues. In our case, using deban/buster, including python3-dev solved the issue. Let me know if you'd like this to be included somehow else, or if I've busted something else in the attempt to fix the issue.

Signed commits

• Yes, I signed my commits.

[Ulincsys]

LGTM

[sgoggins]

Resolves issue #2676 #2677